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Tdvf wave1.v9 #2018

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@mxu9 mxu9 commented Sep 28, 2021

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mxu9 added 2 commits Sep 28, 2021

Previously OvmfPkg/ResetVector uses the Main.asm in
UefiCpuPkg/ReseteVector/Vtf0. In this Main.asm there is only Main16
entry point.

This patch-set is to introduce Intel TDX into Ovmf. Main32 entry point
is needed in Main.asm by Intel TDX. To reduce the complexity of Main.asm
in UefiCpuPkg, OvmfPkg create its own Main.asm to meet the requirement
of Intel TDX.

UefiCpuPkg/ResetVector/Vtf0/main.asm -> OvmfPkg/ResetVector/Main.asm

Cc: Ard Biesheuvel <>
Cc: Jordan Justen <>
Cc: Gerd Hoffmann <>
Cc: Brijesh Singh <>
Cc: Erdem Aktas <>
Cc: James Bottomley <>
Cc: Jiewen Yao <>
Cc: Tom Lendacky <>
Signed-off-by: Min Xu <>

Previously WORK_AREA_GUEST_TYPE was cleared in SetCr3ForPageTables64.
This is workable for Legacy guest and SEV guest. But it doesn't work
after Intel TDX is introduced. It is because all TDX CPUs (BSP and APs)
start to run from 0xfffffff0, thus WORK_AREA_GUEST_TYPE will be cleared
multi-times if it is TDX guest. So the clearance of WORK_AREA_GUEST_TYPE
is moved to Main16 entry point in Main.asm.
Note: WORK_AREA_GUEST_TYPE is only defined for ARCH_X64.

For Intel TDX, its corresponding entry point is Main32 (which will be
introduced in next commit in this patch-set). WORK_AREA_GUEST_TYPE will
be cleared there.

Cc: Ard Biesheuvel <>
Cc: Jordan Justen <>
Cc: Gerd Hoffmann <>
Cc: Brijesh Singh <>
Cc: Erdem Aktas <>
Cc: James Bottomley <>
Cc: Jiewen Yao <>
Cc: Tom Lendacky <>
Signed-off-by: Min Xu <>
@mxu9 mxu9 force-pushed the tdvf_wave1.v9 branch 3 times, most recently from c8b05f9 to 6054b94 Compare Sep 28, 2021
mxu9 added 2 commits Oct 12, 2021

In TDX when host VMM creates a new guest TD, some initial set of
TD-private pages are added using the TDH.MEM.PAGE.ADD function. These
pages typically contain Virtual BIOS code and data along with some clear
pages for stacks and heap. In the meanwhile, some configuration data
need be measured by host VMM. Tdx Metadata is designed for this purpose
to indicate host VMM how to do the above tasks.

More detailed information of Metadata is in [TDVF] Section 11.

Tdx Metadata describes the information about the image for VMM use.
For example, the base address and length of the TdHob, Bfv, Cfv, etc.
The offset of the Metadata is stored in a GUID-ed structure which is
appended in the GUID-ed chain from a fixed GPA (0xffffffd0).

In this commit there are 2 new definitions of BFV & CFV.
Tdx Virtual Firmware (TDVF) includes one Firmware Volume (FV) known
as the Boot Firmware Volume (BFV). The FV format is defined in the
UEFI Platform Initialization (PI) spec. BFV includes all TDVF
components required during boot.

TDVF also include a configuration firmware volume (CFV) that is
separated from the BFV. The reason is because the CFV is measured in
RTMR, while the BFV is measured in MRTD.

In practice BFV is the code part of Ovmf image (OVMF_CODE.fd). CFV is
the vars part of Ovmf image (OVMF_VARS.fd).

Since AMD SEV has already defined some SEV specific memory region in
MEMFD. TDX re-uses some of the memory regions defined by SEV.
 - MailBox : PcdOvmfSecGhcbBackupBase|PcdOvmfSecGhcbBackupSize
 - TdHob   : PcdOvmfSecGhcbBase|PcdOvmfSecGhcbSize


Cc: Ard Biesheuvel <>
Cc: Jordan Justen <>
Cc: Gerd Hoffmann <>
Cc: Brijesh Singh <>
Cc: Erdem Aktas <>
Cc: James Bottomley <>
Cc: Jiewen Yao <>
Cc: Tom Lendacky <>
Signed-off-by: Min Xu <>

Intel's Trust Domain Extensions (Intel TDX) refers to an Intel technology
that extends Virtual Machines Extensions (VMX) and Multi-Key Total Memory
Encryption (MKTME) with a new kind of virutal machines guest called a
Trust Domain (TD). A TD is desinged to run in a CPU mode that protects the
confidentiality of TD memory contents and the TD's CPU state from other
software, including the hosting Virtual-Machine Monitor (VMM), unless
explicitly shared by the TD itself.

Note: Intel TDX is only available on X64, so the Tdx related changes are
in X64 path. In IA32 path, there may be null stub to make the build

This patch includes below major changes.

1. Ia32/IntelTdx.asm
IntelTdx.asm includes below routines used in ResetVector
 - IsTdx
   Check if the running system is Tdx guest.

 - InitTdxWorkarea
   It initialize the TDX_WORK_AREA. Because it is called by both BSP and
   APs and to avoid the race condition, only BSP can initialize the
   WORK_AREA. AP will wait until the field of TDX_WORK_AREA_PGTBL_READY
   is set.

 - ReloadFlat32
   After reset all CPUs in TDX are initialized to 32-bit protected mode.
   But GDT register is not set. So this routine loads the GDT and set the
   CR0, then jump to Flat 32 protected mode again. After that CR4 and
   other registers are set.

 - InitTdx
   This routine wrap above 3 routines together to do Tdx initialization
   in ResetVector phase.

 - IsTdxEnabled
   It is a OneTimeCall to probe if TDX is enabled by checking the

 - CheckTdxFeaturesBeforeBuildPagetables
   This routine is called to check if it is Non-TDX guest, TDX-Bsp or
   TDX-APs. Because in TDX guest all the initialization is done by BSP
   (including the page tables). APs should not build the tables.

 - TdxPostBuildPageTables
   It is called after Page Tables are built by BSP.
   byte[TDX_WORK_AREA_PGTBL_READY] is set by BSP to indicate APs can
   leave spin and go.

2. Ia32/PageTables64.asm
As described above only the TDX BSP build the page tables. So
PageTables64.asm is updated to make sure only TDX BSP build the
PageTables. TDX APs will skip the page table building and set Cr3

3. Ia16/ResetVectorVtf0.asm
In Tdx all CPUs "reset" to run on 32-bit protected mode with flat
descriptor (paging disabled). But in Non-Td guest the initial state of
CPUs is 16-bit real mode. To resolve this conflict, BITS 16/32 is used
in the ResetVectorVtf0.asm. It checks the 32-bit protected mode or 16-bit
real mode, then jump to the corresponding entry point.

Cc: Ard Biesheuvel <>
Cc: Jordan Justen <>
Cc: Gerd Hoffmann <>
Cc: Brijesh Singh <>
Cc: Erdem Aktas <>
Cc: James Bottomley <>
Cc: Jiewen Yao <>
Cc: Tom Lendacky <>
Signed-off-by: Min Xu <>
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@mergify mergify bot commented Oct 24, 2021

PR can not be merged due to conflict. Please rebase and resubmit

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